1. Field of the Invention
The present invention relates to a technique for cutting an electrical wiring line disposed beforehand on a substrate, and more particularly, to a technique which cuts, for isolation, electrical wiring lines one from another which have been shorted to each other to avoid static breakdown, in the manufacturing process of an electronic device such as a display device of liquid-crystal or organic electro-luminescence (EL), or a semiconductor device.
2. Description of the Related Art
Electronic devices, such as a liquid-crystal display device and a semiconductor device, are subject to a breakdown due to static in the manufacturing process thereof. To avoid a breakdown due to static electricity, predetermined electrical wiring lines on a substrate on which a driver IC is to be mounted are shorted by a shorting line until the driver IC is mounted on the substrate. Immediately prior to the mounting of the driver IC, the shorting line is cut using a laser or the like so that the electrical wiring lines are isolated from each other (See the first embodiment and FIG. 1 in Japanese Unexamined Patent Application Publication 1-230020, for example).
Since the cutting of each of the electrical wiring lines or the shorting line is carried out at one location only, the isolation of the lines from each other is not fully assured because of dirt sticking to the lines or wiring defects. To avoid such isolation failure between the lines, a cutting operation may be repeated. However, repeated cutting operations lead to prolonged process time. When a substrate bearing a plurality of liquid-crystal panels is diced to a product size, the electrical wiring lines are also cut for isolation at the same time. Such a dual-purpose operation becomes impossible, depending on the shape and the structure of the liquid-crystal panel.
Accordingly, it is an object of the present invention to provide a method and an apparatus for reliably cutting electrical wiring lines formed on a substrate to isolate one line from another in a short period of time.
It is another object of the present invention to provide a method and an apparatus which manufactures an electronic device using the method and the apparatus for cutting the electrical wiring lines.
In one aspect of the present invention, a method of cutting an electrical wiring line or a substrate includes the steps of branching a laser beam into a plurality of branch beams, and directing the plurality of branch beams to the electrical wiring line on the substrate to concurrently cut the electrical wiring line at a plurality of locations. In this way, one electrical wiring line is reliably cut for isolation, and the process efficiency of the substrate is heightened.
The electrical wiring line may be cut by relatively moving the substrate and the branch beams with respect to each other. The electrical wiring line is reliably cut even if the electrical wiring line has a wide line width or even if a plurality of electrical wiring lines need to be cut.
The branch beams may be relatively moved with respect to and perpendicularly to the electrical wiring line. With this arrangement, isolation is reliably assured because the electrical wiring lines are cut at locations according to the number of branch beams.
An angle xcex8 may fall within a range equal to or greater than zero degree and smaller than 90 degrees where the angle xcex8 is formed between a direction of the row of the plurality of branch beams and a direction of the electrical wiring line. In this way, the positions of cutting by the branch beams can overlap with each other, thereby assuring isolation.
The branch beams may be directed to the electrical wiring line on the substrate from the side of a surface thereof having the electrical wiring line. Alternatively, the branch beams may be directed to the electrical wiring line through the substrate from the opposite side to the surface having the electrical wiring line. Furthermore, the branch beams may be directed to the electrical wiring line through the substrate when the electrical wiring line is disposed between a plurality of substrates. To irradiate the electrical wiring line with the laser beam through the substrate, the substrate is required to have a transparency to the laser beam. Experiments show that the cutting of the electrical wiring line by the laser beam transmitted through the substrate not only saves energy more than the direct laser beam irradiation to the electrical wiring line, but also results in a cut portion neater than that resulting from the direct laser beam irradiation to the electrical wiring line.
Preferably, debris resulting from cutting of the electrical wiring line is sucked in while the electrical wiring line is cut. This arrangement prevents the debris from scattering over the substrate.
The laser beam in an infrared light region may be used. The laser beam in the infrared light region is transmitted through silicon.
The laser beam may be generated by a solid-state laser device, a harmonic oscillation of the solid-state laser device, a gas laser device or metal vapor laser device.
The atmosphere for a cutting process may have a pressure lower than the atmospheric pressure. In this arrangement, the generation of dross and debris is effectively suppressed.
The atmosphere for a cutting process may contain no oxygen, or may contain nitrogen or a noble gas. In this arrangement, oxidation of the wiring line is avoided.
The substrate may have a transparency to the laser beam. For example, the substrate may be made of glass or silicon.
A portion of the electrical wiring line to be cut may linearly extend. In this arrangement, controlling the irradiation of the electrical wiring line with the branch beams becomes easy, and process efficiency is heightened.
When electrical wiring lines formed on the substrates of a plurality of electronic devices are cut, the plurality of electronic devices may be juxtaposed to each other so that cut ends of the electrical wiring lines of the respective electronic devices are aligned in a line. In this arrangement, the branch beams are relatively and linearly moved with respect to the cut portions of the electronic devices, so that the irradiation of the electrical wiring lines with the branch beams is easily controlled, and process efficiency is heightened.
The electrical wiring line may be formed on a transparent layer. The transparent layer may be made of ITO or tantalum pentoxide. When the electrical wiring line is irradiated with the laser beam from the opposite side to the surface having the electrical wiring line, the cut area is neater in the case of the wiring line formed on the transparent layer than in the case without the transparent layer, according to the results of experiments.
The electrical wiring line may be made of chromium or ITO.
In another aspect of the present invention, a method for manufacturing an electronic device having a substrate on which a plurality of electrical wiring lines are formed, includes a step of isolating each of electrical wiring lines from another by cutting the electrical wiring lines, wherein the electrical wiring lines are cut using one of the above-referenced methods of cutting an electrical wiring line.
An IC to be connected to the electrical wiring lines may be mounted on the substrate subsequent to the cutting of the electrical wiring lines. In this arrangement, the electrical wiring lines are reliably isolated from each other.
The electronic device may be a display for example.
In yet another aspect of the present invention, an apparatus for cutting an electrical wiring line includes a laser generator for generating a laser beam, an optical beam branching element for branching the laser beam generated by the laser generator into a plurality of branch beams, and a beam condenser for condensing the branch beams branched by the optical beam branching element. A single electrical wiring line is concurrently cut at a plurality of positions, and isolation is assured. Similarly, a plurality of wiring lines are cut by relatively moving the branch beams with respect to the electrical wiring lines.
The optical beam branching element may also serve as the beam condenser.
The optical branching element may be one of an optical diffraction element and a phase grating.
The apparatus may further include a beam splitter element for splitting the laser beam generated by the laser generator into a plurality of beams, wherein the optical beam branching element is arranged at least for one split beam. In this arrangement, the process efficiency is further heightened.
The beam splitter element may be a polarizing beam splitter.
The apparatus may further include a retardation element disposed in front of the polarizing beam splitter, for adjusting a polarization plane component ratio of the beam. In this arrangement, the power of each split beam is finely adjusted.
The apparatus may further include a beam expander for adjusting the beam diameter of the beam prior to beam condensation. This arrangement allows the focal depth of the laser beam to be adjusted, thereby making adjustments to a variation in the position of the cutting operation.
The apparatus may further include a suction mechanism for sucking debris resulting from the cutting of the electrical wiring line. The scattering of the cut debris is controlled.
In a further aspect, the present invention relates to an apparatus for manufacturing an electronic device including a substrate having a plurality of electrical wiring lines to be connected with an IC mounted on the substrate. The apparatus includes a laser generator for generating a laser beam, an optical beam branching element for branching the laser beam generated by the laser generator into a plurality of branch beams, and a beam condenser for condensing the branch beams branched by the optical beam branching element, so that the plurality of electrical wiring lines which are shorted to each other are cut by the branch beams for isolation from each other and then connected with the IC.
The optical beam branching element may also serve as the beam condenser.
The apparatus may further include an IC mounter to mount the IC on the substrate.
An optical system including the laser generator, the optical beam branching element and the beam condenser may be incorporated in the IC mounter. A compact design is thus implemented in the apparatus for manufacturing an electronic device.
The laser generator may be a laser diode oscillator. A compact design is thus implemented in the laser generator.